A Little Thing Called Hope
by NotYourDamsel
Summary: [SI/OC] Kohaku doens't know what's wrong, but he does know one thing—he somehow wound up in the past, with nothing but the clothes on his back and his camera, in a world where demons are apparently real, and now he's someone called a 'marechi', whatever that is. He just wants to go back home and watch anime, dammit!


**Summary**: Kohaku doens't know what's wrong, but he does know one thing—he somehow wound up in the past, with nothing but the clothes on his back and his camera, in a world where demons are apparently real, and now he's someone called a 'marechi', whatever that is. He just wants to go back home and watch anime, dammit!

**Warnings**: Slash, Time Travel, AU, Demons, Canon Typical Violence, Blood and Gore, Possible Smut/Explicit Sex, Language, Muzan, Inosuke, Death, etc.

**Disclaimer**: If I owned Kimetsu no Yaiba (SPOILER), RENGOKU OR SHINOBU WOULDN'T HAVE DIED, DAMMIT ALL—

* * *

If somebody asked him, Kohaku was going to blame the stupid kid and his soft, bleeding heart.

Really, though. _Curse his bleeding heart!_

It was the typical cliché: kid's ball rolls to the street, dumb kid runs after it without looking, some stupid ass dude with strong moral obligations saves him, the dude dies.

That's exactly what happened to Kohaku, who was coming home from school.

He didn't even pause to think—all that was in his head was this kid was going to get killed, then BAM! His legs pushed towardsa and barreled the dumb kid out of the way.

Being hit by a truck hurt like a bitch.

Kohaku's final thought was wondering if his camera survived the impact. It was from his late grandfather, and he made a lot of good memories with it.

.

* * *

He died. But of course, he didn't stay dead.

Like, what the actual fuck _Shinigami_?

* * *

.

The next time he woke up, he was still wearing his (bloody) hoodie plus jeans ensemble, his (thankfully unbroken) camera still hung around his neck from its strap, and staring at the sky.

_It looks wrong_, he thought.

He didn't know what made him think of that. Maybe it was the shade of blue that was just a tad too clear. Maybe it was how white and pure the clouds looked like. Maybe it was the fact that it should be almost sunset, not the middle of the day.

He sat up, miraculously devoid of any injuries when he was sure he flew at least three feet away from the impact alone. Dusting his pants free from any grass, he looked around the forest he ended up in, and cocked a head.

_Wrong, everything feels off and wrong._

(But why?)

Kohaku rubbed the back of his head, eyebrows furrowed and a slight frown playing on his lips. With no other choice, he decided to wander around and hopefully find someone.

That's when things started to get weird. Well, weirder. But still.

He did find a village, after descending the mountain. But it was the kind of village that you see in paintings and movies: traditional and old, made from wood and paper _shogi_ doors. The people there were dressed in _yukatas_ and _haoris_, with sandals and hair ornaments adorning their heads. They looked at him strangely, with his modern clothes, and he looked straight back, baffled and dread coiling around his stomach.

When he asked a kind, elderly lady what date it was, he finally confirmed his worst fear.

He was in the past, with no way back to his present.

* * *

.

The grandma—Setsuko-_baachan_—was kind enough to let him stay, so long as he chopped the wood and did some odd-jobs here and there. He learned more as he went. He learned how to weave a sturdy basket with bamboos, he learned the most efficient way to plow fields, he learned how to mend his clothes quickly instead of buying new ones, and he learned how to weild a _naginata_ from Shiro-_ojisan_.

His naginata, made and struck by Kamashiro-_san_ himself, was beautiful in a deadly sort of way. One blade was dyed a dark red, with the engraving of a phoneix on it, its tails painted orange, yellow and gold on the naginata's body. The other blade, the typical silver hue, was carved with two simple kanji.

**希望**

Hope. A reminder, a promise.

Everything was going well: he had a nice family he could depend on, a group of friends and comrades he wouldn't hesitate in calling for help, sunshine and good weather, and an ember of hope that burned in his chest.

Then the disappearances started.

* * *

.

Mt. Natagumo has always starred in numerous horror stories, urging children to go to sleep early and never wander out at night. Or the demons would gobble them all up and everything they loved.

Morbid, but true. Plus, it helped keep the brats in check.

People were slowly disappearing as they went up Natagumo. Never coming back, leaving the villagers ansty and worried. Even fearful.

Kohaku wouldn't have minded it. He would've ignored it, if it weren't for idiot Shigure to become lost as well.

The night after that, he set off for Natagumo.

(He knows he should have listened to Setstuko-_baachan_, but he needed to know what happened to sweet, carefree Shigure. He needed to know what took him from them all)

Clad in a yellow _yukata_ and burnt orange _haori_ with black and white linings, he went up the steep mountain, his trusty _naginata_ (whom he had lovingly named as Akari) strapped on his back and a determined scowl on his face.

The months that had left him working his body harder than before had made him stronger, with rough palms and steady limbs. He could take down a boar barehanded with his mind and newfound strength, but he always kept in mind the knowledge that there are people stronger than him, that there are literal demons that could rip him into shreds with nary a thought. The journey was long, trecherous and hard. Air was thinner uphill, and it took Kohaku longer than he would have liked to reach at least the middle part of Natagumo.

There, he met a little boy that was anything but.

(There, Kohaku changed the tides and said goodbye to Fate and all of her plans)

* * *

.

His name was Rui, and he wasn't normal.

He could tell by his pale complexion, the color of his hair, and the markings on his face. He didn't need to see the spiders to find out his true nature.

He was a demon. A killer. A man-eater.

(He was the one who took Shigure away)

But he was lonely. So, so utterly _lonely_ that Kohaku could feel it in his bones, could feel the heartwrenching cries the boy's dead heart made.

He couldn't use Akari against him. Not against the boy who sought nothing but warmth. Who wanted a bond forged with trust and love among any other.

It was stupid, it was likely to get him killed. And he blamed his bleeding heart once again.

He extended a hand, and smiled.

"Why don't I be your family instead?"

* * *

.

Of course, it wasn't easy.

There was talking, there was dodging, there was more nearly dying than Kohaku could put up with. But now they were on speaking terms, without any puppetering or webbing that held his limbs to prevent any attacks or escapes.

He asked him questions, and Rui sometimes answered them. Where he came from (he didn't know), who his parents were (none either), what his favorite food was (adults, apprently), what his favorite game was (perhaps tag, it was enjoyable seeing them scuttle about hopelessly before dying miserable deaths), and so on.

He was making progress at a snail's pace, but it was progress nevertheless. He even got to meet the rest of his 'family', which were unsure on how to treat the food they were not suppoused to eat.

Then, when one of his 'older sisters' attempted to run away, Kohaku stopped him.

* * *

.

"What are you doing, Kohaku-_nii_."

The title was warm, but Rui's face was as expressionless as ever. Kohaku knew, that in his eyes, he was the perfect older brother. Kind, accepting, strong, and ever-patient. But that didn't mean he wouldn't kill him. Not when he wasn't playing his role, or whatever that was.

Kohaku smiled, and Rui's shoulders slumped.

They both knew who won and lost.

"You don't have to kill her, _otouto_," Kohaku whispered, arms wide and weapon nowhere in sight. "It's just like her going on a trip, but she'll return and bring back some souveniers. _Ne_, _imouto_?" He looked at the 'eldest daughter', who nodded at him gratefully. A compromise, that was all he could do for now. He wasn't close to Rui as much as he wanted to, but maybe someday, he could stop him from eating people and enslaving demons to become his 'family'. Well, he could let him eat criminals, but that was for another day.

Rui watched them both quietly, the gears turning in his mind. His other 'older sister', the snitch, watched the proceedings nervously.

Then Rui nodded, and that was that.

("Don't do that again," the little boy murmured, tucked perfectly at his side in their shared futon. It was daylight, but yesterday's meeting had tired him, and Kohaku didn't mind a little bir of cuddling.

He kissed his forehead, and pretended to not see his wide, wary eyes filled with hope. "No promises, Rui.")

* * *

.

Life with demons was... strange, but not uncomfortable.

He learned that 'father' often liked to take walks when he was human, it was how he met Rui, after all. He found out that 'mother' was merely a teen, and that she abhorred cucumbers with a passion. He learned that his 'older brother' liked to paint, which made him buy some paper and dye for him to play with and experiment. His younger siblings merely like his songs, songs that were from his original timeline that carried messages and feelings mere words couldn't express. He learned that his 'younger sisters' truly loved eachother as siblings, and were trying to fix the schism from their escape turned wrong.

Then he learned of Rui's Master. The one who 'saved him' one, April night.

* * *

.

He felt him before he even saw him. Heavy and dark and ridiculously powerful.

When he first saw him, red eyes and all, he blurted out the first thing that came into his mind:

"Michael Jackson?"

The demon blinked, then asked, "Pardon?"

Kibitsuji Muzan was his name. Though he looked eerily like Michael Jackson. Were they related or something? Does this mean Michael Jackson's part demon?

Can demons even reproduce?

Turns out, Muzan was curious of the human Rui had adopted, in a way. And wondered why he wasn't turned into a demon yet.

"Well, who would buy Kiyoshi's paint? Who would go to the market for some fresh fruits and vegetables? Who would do the laundry and hang it out to dry?"

Muzan had looked at him strangely at that, as if he was some new species he'd just discovered.

He began visiting bi-weekly after that, usually coming at the dead of night and staying as late (or early) as three in the morning. He was surprisingly pleasant to talk to, despite being the demon. He knew about a lot of things, from his centuries of living. And he wanted to know more about human culture too, which was probably for hiding purposes, but Kohaku was more than happy to help.

Then he noticed his camera, and asked what it was.

"Oh, this?" He held up his camera, which was amazingly still filled with energy from the... year and a half that he was stuck here in this era. "This is called an instant camera, or instax, for short. Here." He positioned it on his left eye, and called out, "Smile!" before clicking the button.

Muzan sat there, stock-still in wonder and apprehension, as a square piece of _something_ was coming out from the gash on the 'instant camera' his human companion had. Kohaku took the picture, and started flapping it to dry the ink. Grinning at the result, he handed it to the bemused demon and laughed at his gobsmacked expression.

"Pretty neat, huh?"

Muzan only nodded silently, still staring at awe from his picture. It looked exactly like him! Did humans really invent this? Then how come he's never seen it before in Tokyo?

Kohaku laughed sheepishly at that. "I'm, uh... from the future?"

Muzan stared at him. "Explain." And he did.

The result was Muzan rubbing the bridge of his nose as he sighed, and Kohaku offered a massage which was declined. The revelation didn't do anything with their friendship, which was good, because Kohaku liked talking to Muzan, no matter how crazy that sounded. He started asking about how the future looked like, and was speechless at the inventions humans would soon make. Carriages running on 'fuel'? Flying trains? Lamps that can be turned on and off with a 'switch'? Harnessing electricity?

"It would be a pleasure to see that all happening," the ravenette breathed out, red irises sparkiling. Kohaku laughed. "Yeah, but you should probably head to Europe—that's in the far West, 'cause that's where it all started." He smiled, and said, "As for me, I'd probably be long dead before that happens."

"Then become a demon."

Kohaku shot Muzan a flat look. "Yeah, no. My answer won't change, Muzan."

He laughed when Muzan sulked. Wait, _brooded_. Yeah, Muzan _brooded_ in the corner.

Rui didn't know what to even think.

* * *

.

It all happened when Kohaku got a scratch.

It was a papercut, really. But Muzan's eyes had dilated and he shot forward to grasp his bleeding finger to—

"W-What the hell, Muzan!?" Kohaku yelped, as his demonic friend started lapping on the wound feverently, struggling to escape under his hold.

An honest to _Kami_ **moan** answered him, and Muzan panted heavily as he sucked on his finger like a thirsty man in a desert.

Kohaku didn't know what in the name of Amaterasu was happening, but it was making him feel weird and _damn his bisexual hormones!_

"M-Muzan," he whimpered, and shivered when lidded, dark garnets looked up at him in a smoldering way. He swallowed thickly, and gasped out, "What are you doing?"

Muzan hummed, giving his finger one last, long lick before sitting up straight, pulling him on his lap as if it was an everyday occurence. Kohaku clamped down the urge to scream.

"You're a _marechi_, Kohaku," he muttered, fondly caressing his cheeks like one would to a lover. A smirk bloomed in his features upon seeing his face turn beet red from the action. "A _marechi_ is someone whose blood contains more power than five humans combined. In short, a feast for us demons." His red eyes gleamed malevolently, and he buried his nose on the crook of Kohaku's neck. That bastard knew he was fucking sensitive there!

"But you," he inhaled, and exhaled in a dreamy manner. It was both creepy and cute. "You, dearest Kohaku, your blood is more powerful than a hundred combined. The scracest of _marechis_ that I have ever consumed."

He ran his tongue slyly on his neck, and chuckled at the groan that escaped him. Kohaku badly wanted to **punch** him. Or _fuck_ him. Either way works. Really.

"S-So? What does that have to do with you—_gaah!_"

_The motherfucking bastard bit his Adam's apple! What the actual fuck, Muzan!?_

Grabbing black, curly locks harshly, he pulled Muzan's face away and glared at the mildly shocked demon.

"If you want my blood so much, you can just fucking ask instead of molesting me, dammit!"

Muzan stared at him uncomprehensingly for a few moments, before bringing up his hand to rest on the flustered human's cheek.

"But what if I wanted you? Your mind, body and soul?" He narrowed his unearthly eyes. Kohaku struggled not to gape. _What? _"What if I asked for your entirety and everything, Kohaku?" He leaned forward, at least an inch away from kissing him, and whispered silkily,

"What if I wanted to mark you as _mine_, in every bone, blood and flesh? Would you still give it to me, if I asked ever so nicely?"

Kohaku did the most logical thing to do.

He headbutted the motherfucking bastard.

* * *

.

Muzan didn't visit for a while after that... incident.

Kohaku didn't know if he was giving him space, was ashamed, scared or mad, but it felt lonely to not have midnight talks with him. Felt almost wrong to not feel his body beside his.

Rui was sad, too. Because he wanted his 'older brother' to be happy.

When he came back (after two, _kami_forsaken long weeks!), Kohaku made sure to plummet him into the ground with his pillow and fists, before kissing the living daylights out of that egoistical demon who just had to make him fall deeply in love.

It wasn't the greatest of kisses, with Kohaku fumbling and hitting the other's fangs (dear _kami_, what if his tongue gets torn by them?), but Muzan had smoothly taken lead, and was practiclally eating his mouth by the time they hit the wall, far too gone in their lust to notice anything around them.

"Mine," Muzan growled, sucking harshly in a patch of skin on his collarbone. "My _marechi_, my human."

"Yours," Kohaku mewled, wrapping his legs around his waist as Muzan grinded their manhoods together.

Muzan pulled him into another kiss, demanding and wanting in all possible ways. Kohaku was more than happy to give it to him.

* * *

**Soo... that happened. Heh. I just finished watching the whole season one today, and wanted to write down a fanfic for Muzan Jackson and bam! Plotbunny was born.**

**There might be—scratch that, there will be some lemons in the future, but I'll put a warning for those of you who don't like it. Peace.**


End file.
